1. Field of the Invention
This invention pertains generally to laser light sources, and more particularly to plasmon laser light sources.
2. Description of Related Art
Laser science has been successful in producing increasingly high-powered, faster and smaller coherent light sources. Examples of recent advances are microscopic lasers that can reach the diffraction limit, based on photonic crystals (Altug, H., Englund, D. & Vuckovic, J. Ultrafast photonic crystal nanocavity laser. Nature Phys. 2, 484-488 (2006)), metal-clad cavities (Hill, M. T. et al. Lasing in metallic-coated nanocavities. Nature Photon. 1, 589-594)), and nanowires (Johnson, J. C. et al. Single gallium nitride nanowire lasers. Nature Mater. 1, 106-110, Duan, X., Huang, Y., Agarwal, R. & Lieber, C. M. Single-nanowire electrically driven lasers. Nature 421, 241-245 (2003)).
However, such lasers are restricted, both in optical mode size and physical device dimension, to being larger than half the wavelength of the optical field, λ/2 (see Bergman, D. J. & Stockman, M. I. Surface plasmon amplification by stimulated emission of radiation: quantum generation of coherent surface plasmons in nanosystems. Phys. Rev. Lett. 90, 027402 (2003), Zheludev, N. I., Prosvirnin, S. L., Papasimakis, N. & Fedotov, V. A. Lasing spaser. Nature Photon. 2, 351-354 (2008)), which illustrate the current understanding in the art that it is a fundamental physical limit of optics that the optical mode size is limited to λ/2 (see Eugene Hecht, “Optics,” Addison Wesley (1987)). It therefore remains a key fundamental challenge to realize ultra-compact lasers that can directly generate coherent optical fields at the nanometer scale, which is far beyond the diffraction limit.
One way of addressing this issue is to make use of surface plasmonswhich are capable of tightly localizing light. However, ohmic losses at optical frequencies have inhibited the realization of truly nanometer-scale lasers based on such approaches (see Ambati, M. et al. Observation of stimulated emission of surface Plasmon polaritons. Nano Lett. 8, 3998-4001 (2008), Noginov, M. A. et al. Stimulated emission of surface plasmon polaritons. Phys. Rev. Lett. 101, 226806 (2008)).
Accordingly, an object of the present invention is a plasmon light source capable of a confined generation of sub-wavelength scale or sized high intensity light.